<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">
    <span v-if="isUser">
        <label for="username">用户账号 </label>
        <!--  通过增加key并设置不同的值,来清空上一次输入的内容-->
        <input type="text" id="username" placeholder="用户账号" key="username">
    </span>
    <span v-else>
        <label for="email">用户邮箱 </label>
        <input type="text" id="email" placeholder="用户邮箱" key="email">
    </span>
    <button @click="isUser=!isUser">切换类型</button>
</div>
<script src="../js/vue.js"></script>
<script>

    const app = new Vue({
        el: "#app",
        data: {
            msg: "hello",
            isUser: true
        },
    })
</script>

</body>
</html>
